A voltage regulator is a circuit to output a predetermined output voltage based on a power supply voltage supplied from outside. Characteristics of the voltage regulator are deteriorated in accordance with change in an external operation environment such as a temperature or a frequency of a ripple of the power supply voltage.
As the temperature rises, the voltage regulator becomes oscillated easily, and an overshoot of the output voltage which occurs at the time of rising of the output voltage, and an undershoot which occurs at the time of falling of the output voltage are respectively increased. Further, as the frequency of the ripple of the power supply voltage is increased, the ripple is increased in the output voltage of the voltage regulator.